The Great Animal Migrations

Journeys Across the World

Every year, all over the world, millions of animals set off on incredible journeys. Birds fly across whole oceans. Herds of huge animals thunder across the plains. Tiny butterflies flutter for thousands of kilometres. Fish swim up rushing rivers. These amazing journeys are called migrations.

To migrate means to travel a long way from one place to another, and usually back again, as the seasons change. Animals do not migrate just for fun. They make these difficult and dangerous journeys because they have to, in order to survive.

In this book we will discover why animals migrate, how they find their way across such huge distances, and meet some of the world's greatest animal travellers. Pack your bags — we are going on a journey.

Why Animals Migrate

Why would an animal leave its home and travel so far? There are three main reasons.

The first reason is food. In many places, food is easy to find in the warm months but disappears in winter when plants stop growing or the ground freezes. Rather than starve, animals travel to places where food is still plentiful.

The second reason is weather. Winter can be deadly. Many animals migrate to warmer places to escape the cold, then return when spring arrives. Birds that cannot find insects in a frozen land fly south to where the weather is kind.

The third reason is having babies. Some animals travel to special places that are safe for raising their young, with plenty of food and fewer dangers. Once the babies are big and strong, the family makes the journey back.

So migration is all about survival: finding food, escaping harsh weather, and keeping the next generation safe.

Finding the Way

One of the greatest mysteries of migration is how animals find their way. Some travel thousands of kilometres across land and sea, often to places they have never seen, without ever getting lost. How do they do it?

Animals use many clues. During the day, some follow the position of the sun in the sky. At night, some use the stars, just as sailors once did. Many follow landmarks like rivers, mountains and coastlines to guide them.

Most amazing of all, many animals can sense the Earth's magnetic field. Our planet is like a giant magnet, with invisible lines running between the north and south. Some birds, turtles and even insects can feel these lines, using them like a built-in compass to know which way to go.

Animals also have an incredible sense of timing. As the days grow shorter or the weather changes, something inside them tells them that it is time to set off. Many young animals make their first journey alone, finding the way by instinct, without anyone to teach them.

The Great Wildebeest March

One of the most spectacular migrations on land happens every year in Africa. Across the grasslands, more than a million wildebeest — large, horned animals a bit like cattle — travel together in an enormous herd, along with thousands of zebras and gazelles.

They are following the rains and the fresh green grass. As the dry season turns one part of the grassland brown and bare, the herds move on to find new grass growing where the rain has fallen. Round and round they go in a great circle that takes a whole year.

The journey is full of danger. The wildebeest must cross wide rivers where hungry crocodiles wait, and lions stalk the herds on the plains. But by travelling together in such huge numbers, many of them make it through. Along the way, calves are born and quickly learn to run with the herd.

Birds of the Sky

Birds are the champions of migration, and the skies fill with travellers as the seasons turn. When winter comes to the cold north, billions of birds fly south to warmer lands, then return in spring to nest.

Some birds make astonishing journeys. The tiny swallow flies between Europe and Africa every year. Geese fly in a neat V-shape, which helps them save energy: each bird rides on the easier air left by the one in front, and they take turns leading.

The greatest traveller of all is the Arctic tern. This seabird flies all the way from the Arctic at the top of the world to the Antarctic at the bottom — and back again — every single year. Over its lifetime, an Arctic tern flies far enough to reach the moon and back several times. No other animal travels so far.

The Butterfly That Crosses a Continent

It is amazing enough that big, strong animals migrate, but some of the greatest travellers are tiny and delicate. The monarch butterfly of North America makes one of the most wonderful journeys in nature.

Each autumn, millions of monarch butterflies leave the cooler north and fly thousands of kilometres south to a warm forest where they spend the winter. So many gather there that the trees turn orange with their wings.

Here is the truly amazing part. The journey is so long that no single butterfly lives to make the whole round trip. It takes several generations — parents, children and grandchildren — to complete the full circle. Yet somehow the great-grandchildren find their way back to the very same forests their great-grandparents left, guided only by instinct.

Travellers of the Sea

The oceans are full of migrating animals too, swimming vast distances through the water.

Great whales, like the humpback, spend the summer feeding in cold seas near the poles, where food is rich. In winter they swim thousands of kilometres to warm waters near the equator, where they have their calves in calm, safe seas.

Salmon make a remarkable journey of their own. They are born in rivers, then swim out to live in the sea. Years later, they return to the very same river where they were born to lay their eggs, often leaping up waterfalls and swimming against the rushing current to get there.

Even sea turtles migrate. They swim across whole oceans, then return to the same beach where they hatched to lay their own eggs in the sand, finding their way by sensing the Earth's magnetism.

The Dangers of the Journey

Migration is amazing, but it is also hard and dangerous. Travelling animals face many challenges along the way.

They must avoid predators waiting to catch them, like the crocodiles at the river or the falcons in the sky. They face bad weather, such as storms that can blow birds off course. And they must find enough food and rest along the route to keep up their strength for the long way ahead.

People can make migration harder, too. Buildings, roads and fences can block the paths animals have used for thousands of years, and a loss of safe resting places leaves them tired and hungry. By protecting the special places where migrating animals stop to rest and feed, we can help these great travellers complete their journeys.

What We Learned

What an incredible journey we have been on! Let's remember what we found.

Migration means travelling a long way and back as the seasons change, and animals do it to find food, escape harsh weather, and reach safe places to raise their young. To find their way, they use the sun, the stars, landmarks and even the Earth's magnetic field, often guided by instinct alone. We followed the wildebeest across Africa, soared with the record-breaking Arctic tern, marvelled at the monarch butterfly's journey across many generations, and swam with whales, salmon and sea turtles.

The great animal migrations are among the most amazing events in all of nature. When we understand them, we can help keep these wonderful journeys going for years to come.

Want to discover more about the living world? Travel the globe in Amazing Animals of the World, or explore the ocean in Explorers of the Deep Sea.